A variety of modern machine tools, such as lathes, screw machines, automatic machining centers, etc. employ indexable turret devices for presenting a succession of cutting tools to the work piece for the performance of various machining operations. Quite typically, a specific machined part will require a plurality of machine operations to be performed in succession, such as sizing, threading, undercutting, chamfering etc. The necessary tools for each of these operations are mounted in the several index positions of a turret and presented to the work piece in the desired succession by periodic indexing of the turret.
Conventional indexable turret devices are normally self-actuated, typically by dedicated hydraulic or electrical mechanisms, such that the indexable turret mechanism as a whole is customarily a complex and costly element of machine tool.
In accordance with the present invention, a novel indexable turretlike device is provided, which is passive in nature and is indexed by external means. To greatest advantage, the mechanical motions necessary to effect indexing are derived from movements of the tool holding slide, which are already available on the machine for the normal manipulation of cutting tools and which can be easily controlled to perform the motions necessary for indexing by conventional numerical control facilities, for example.
In a particularly simplified form of the invention, a fixed plunger-like indexing element is mounted on the headstock, ram or other tool supporting element of the machine. When it is desired to effect an indexing movement, the indexable device is manipulated by programmed movements of the N/C controlled tool support, to move the indexable devices toward and into contact with the indexing element. An indexing plunger, mounted in the turret device, is depressed by the fixed indexing element and executes the necessary mechanical movements to index the turret-like device through one position.
Although the indexable turret-like device of the invention may be used as the principal turret in a simplified machine tool, it may also be used to special advantage when mounted in an individual tool position of a primary, self-actuated turret in an otherwise conventional machine or as an exchangeable tool element in an automatic machining center. By way of example only, if one of several tools, for a multi-tool machining operation, is subject to a much greater rate of wear and replacement than the others, it is possible to mount a plurality of such cutting tools on an externally actuated turret-like device according to the invention, which device is mounted in an individual tool position on a conventional turret. This permits rapidly worn cutting tools to be renewed by merely indexing the passive turret-like device, without stopping the equipment for changing of tools and without limiting the usefullness of the main turret by utilizing more than one of its primary tool positions for duplicates of the same wearable tool.
It will be understood, in this respect, that the inherent complexity and cost of a self-actuating turret arrangement would virtually preclude the use of such a turret as an auxiliary device in one of the tool positions of a conventional primary turret device or as a single tool for an automatic machining center. The externally actuated, passive turret device of the invention, on the other hand, is sufficiently small and compact that it can be carried in an individual tool position on a conventional turret or tool changer carrousel. It of course requires no dedicated electrical, hydraulic or other internal mechanical connections, and thus does not require major redesign and reconstruction of the principal turret, as would be the case if the secondary turret were internally actuated.
For a more complete understanding of the above and other features and advantages of the invention, reference should be made to the following detailed description of a preferred embodiment of the invention and to the accompanying drawings.